#include<stdio.h>
#include<stdlib.h>
#include<malloc.h>

#define MaxSize 50
typedef char ElementType;
//typedef enum{ false,true} bool;
typedef int position;
typedef struct {
  ElementType data[MaxSize];
  position top;
}SqStack;
void InitStack(SqStack * &s);
void DestroyStack(SqStack *&s);
bool StackEmpty(SqStack *s);
bool Push(SqStack *&s,ElementType a);
bool Pop(SqStack *s,ElementType &e);
int duiceng(SqStack *&s);
int main()
{
	int i;
	SqStack *s;
	i=duiceng(s);
	if(i==1)
	printf("yes");
	else
	printf("no");
	printf("\n");
	return 0;
}
void InitStack(SqStack * &s)
{
  s=(SqStack *)malloc(sizeof(SqStack));
  s->top=-1;
}
void DestroyStack(SqStack *&s)
{
  free(s);
}
bool StackEmpty(SqStack *s)
{
  return (s->top==-1);
}
bool Push(SqStack *&s,ElementType a)
{
  if(s->top==MaxSize-1)
  return false;
    s->top++;
    s->data[s->top]=a;
  return true;
}
bool Pop(SqStack *s,ElementType &e)
{
  if(s->top==-1)
  return false;
  e=s->data[s->top];
  s->top--;
  return true;
}
int duiceng(SqStack *&s)
{
  int i=0;
  char e;
  char a[MaxSize];
  a[i]=getchar();
  for(i=1;a[i]!='\0';i++)
  a[i]=getchar();
  InitStack(s);
  for(i=0;a[i]!='\0';i++)
  {
    Push(s,a[i]);
  }
  for(i=0;a[i]!='\0';i++)
  {
    Pop(s,e);
    if(a[i]!=e)
    {
      return 0;
    }
  }
  return 1;
}
 
